Ferroelectric films are a promising candidate for scanning probe-based memory storage devices. One fundamental hurdle inherent to this technology is probe wear. Over the lifetime of the memory storage device the probes are expected to scan at high speeds across the surface of the storage medium a total distance of up to 10 kilometers. Throughout this time the probes must maintain a minimum diameter, since the probe tip diameter directly determines the size of the domains that are written. For high density storage, this diameter must be less than 20 nanometers (nm) for early products and will need to be further scaled down for each subsequent technology generation. However, early tests have shown that the probe tips lose their sharpness and degrade significantly under conditions of high speed scanning over long distances. Water vapor is known to act as a lubricant and does indeed reduce tip wear; at 80 percent humidity for example, there is a 50 percent reduction in tip wear versus a dry environment. However, the maximum humidity that can be used is less than 40 percent due to the fact that water condenses on the tip at higher humidities. Such condensation significantly enlarges the effective tip diameter, resulting in larger bits being written.
For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the discussion of the described embodiments of the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements, while similar reference numerals may, but do not necessarily, denote similar elements.
The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Similarly, if a method is described herein as comprising a series of steps, the order of such steps as presented herein is not necessarily the only order in which such steps may be performed, and certain of the stated steps may possibly be omitted and/or certain other steps not described herein may possibly be added to the method. Furthermore, the terms “comprise,” “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. Objects described herein as being “adjacent to” each other may be in physical contact with each other, in close proximity to each other, or in the same general region or area as each other, as appropriate for the context in which the phrase is used. Occurrences of the phrase “in one embodiment” herein do not necessarily all refer to the same embodiment.